Thermopile Presence Detection with Adaptive IR Thresholds
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Solution Overview
Problem
Existing IR sensors, particularly thermopiles, struggle to accurately detect presence in environments with fluctuating background temperatures due to calibration difficulties, leading to false positives and negatives.
Innovation Solution
A dynamic, self-adjusting system that adapts to environmental changes by using a dampening filter and multiple thresholds to minimize false detections, with a first threshold for transitioning from non-present to present and a second threshold for transitioning from present to non-present, based on IR sensor data variability and baseline adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed threshold is used for presence detection, then the system is simple to operate, but false positives and negatives increase in environments with fluctuating background temperatures
Solution Approach 1:
The patent implements dynamic threshold adjustment by continuously calculating the baseline IR signal from recent measurements and adapting the detection threshold based on the variability of background conditions. This allows the system to automatically respond to environmental changes without manual intervention, resolving the contradiction between operational simplicity and detection reliability.
Solution Approach 2:
The system uses feedback from continuous IR measurements to automatically adjust the detection threshold. By monitoring the variability of background IR signals and adapting the threshold accordingly, the system maintains high detection accuracy in fluctuating environments while requiring no manual reconfiguration, thus resolving the contradiction between simplicity and reliability.
2Measurement precision
If the detection threshold is lowered to improve sensitivity, then more presence events are detected, but false positives increase due to background temperature fluctuations
Solution Approach 1:
The patent changes the parameter of the detection threshold from a fixed value to a dynamically adjusted value based on measured background variability. This allows the system to maintain high sensitivity by adapting the threshold to current conditions, while automatically suppressing false positives when background fluctuations increase, thus resolving the contradiction between sensitivity and false alarm reduction.
3Reliability
If the detection threshold is raised to reduce false positives, then reliability improves, but false negatives increase and presence detection becomes less sensitive
Solution Approach 1:
The system dynamically adjusts the detection threshold based on real-time measurement of background IR signal variability. When background conditions are stable, the threshold can be lower for high sensitivity; when variability increases, the threshold automatically raises to reduce false positives. This dynamic adaptation resolves the contradiction between reliability and sensitivity.
4Measurement precision
If manual calibration is performed to adapt to environmental conditions, then detection accuracy improves, but the system complexity and calibration time increase
Solution Approach 1:
The patent implements self-service calibration by automatically calculating the baseline IR signal and adjusting detection thresholds based on measured background variability. The system performs what would traditionally require manual calibration operations automatically, using algorithms that compute baseline values from recent measurements and adapt thresholds accordingly, thus improving accuracy while eliminating manual intervention and reducing system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively reduces false positives and negatives by dynamically adjusting thresholds in response to environmental fluctuations, ensuring reliable presence detection.
Implementation Method 1
using infrared radiation
Implementation Method 2
Thermopiles is an IR sensor that can deliver output as absolute temperature
Data Source
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AI summary
There is provided a method for determining presence of a person comprising a) receiving IR sensor data (50) during a first time period from a thermopile and using the IR sensor data to determine an IR background signal baseline (51) for the time period, and determining a variability of the IR sensor data (50), b) using the IR background signal baseline (51) and the variability of the IR background signal level to determine a threshold (52) with a value higher than the background signal baseline (51), and in such a way so that greater variability in the IR background signal (50) results in a higher threshold (52), then c) receiving further IR sensor data (50) during a second time period, which is after the first time period, and using the further IR sensor data (50), and the threshold (52) determined in step b) to determine that a person is present when the further IR sensor data (50) comprises a value that is higher than the threshold.